Conventional hinges ordinarily comprise leaves including a barrel. The barrel of a conventional hinge comprises two or more knuckles of leaf material rolled into circular loops, the interiors of which, when aligned, constitute a bore to receive a hinge pin.
Known quality hinges provide advantages of strength and durability but at a significant cost in material and manufacturing operations. When doors or other members to be hinged are light and used moderately, hinge strength and durability are of secondary importance.
Various forms of hinges for special application do not use the well-known rolled knuckle. For example, U.S. Pat. No. 4,385,418 describes a special purpose hinged flap for use in a jet aircraft cooling system. To insure security and reliable operation, the hinge components are formed of relatively thick metal. The lug type knuckles are stepped down from each leaf, thus providing leaves thicker than the knuckles by an amount corresponding to the elongation of a hinge pin head to accommodate a slot.